Artikel
C5b-9 upregulation on endomysial capillaries in non-dermatomyositis cases
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Veröffentlicht: | 25. August 2015 |
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Question: Upregulation of the terminal membrane attack complex (MAC) C5b-9 on endomysial capillaries is generally regarded as major diagnostic hallmark of dermatomyositis (DM). Although the underlying pathophysiology is not entirely understood, C5b-9 upregulation seems to lead to microinfarctions and damage of the vascular network. We report on a case series of 19 patients presenting with a C5b-9 accumulation on endomysial capillaries in the absence of clinical or neuropathological evidence for DM and critically evaluate this marker.
Methods: We compared the C5b-9 staining pattern of 19 non-DM patients with 12 DM and 8 control patients. To decipher potential differences in the C5b-9 distribution pattern between DM and non-DM cases, we additionally assessed the extent of endomysial capillary C5b-9 deposits related to the capillary density and extent of myofiber necrosis by immunohistochemistry. Clinical data was added via a telephone follow-up.
Results: Our results show that similar numbers of C5b-9-positive myofibers were present in both DM and non-DM C5b-9+ cases. However, the distribution pattern significantly differed as DM cases showed significantly more perifascicular C5b-9 deposits as compared to non-DM cases, the latter presenting with stronger C5b-9 expression on endomysial capillaries in a diffuse pattern. Of note, the total capillary density did not significantly differ between normal control tissues, DM and non-DM C5b-9+ cases but DM patients displayed significantly more C5b-9+ necrotic fibers as compared to non-DM C5b-9+ and control cases.
Conclusion: In summary, our results show that endomysial capillary C5b-9 deposits are also present in a large variety of non-DM cases with a tendency to autoimmune diseases. However the distribution pattern significantly differed from DM cases. In conclusion, C5b-9+ deposits should only be relied on as an immunohistochemical criterion for the diagnosis of DM if the C5b-9 distribution pattern is taken into consideration.